Expertly
by Cumberbatch Critter
Summary: "Yeah, if it's that easy," John said, crossing his arms, "tell her 'no'." Sherlock blinked down at Lily and her big, blue eyes. He opened his mouth and then closed it again. "Yeah, I don't know that word," he said absently. [Sherlock & John/Mary/Baby Watson (named Lily, in this case) fluff.]


**Expertly**

"No, no, no, no, no!" Sherlock's bare footsteps were muted against the hardwood floor, but an indicator loud enough to the nineteen month toddler running across the room. "No, you aren't!" He swept the toddler off her feet and swung her up under his arm amidst her giggling shrieking. "You are going to have a nappy change."

"Nooooo!"

Sherlock pressed his lips into a thin line to fight against the smile. "Yes. I know it's tedious, but it's necessary. John would never let me hear the end of it if you got a rash. Stop _squirming_!"

"No!"

Sherlock unceremoniously deposited her into her playpen. "Well, I'm your guardian for the day, so what I say goes. Stay there, I'm going to get nappies."

"Nooo!"

Sherlock sighed, but it was theatrical at best. He couldn't help but smile, never-mind that John and Mary's toddler was nearly into her so-called terrible two's and her favourite rebuttal was drawling _No!_ over and over to any living thing nearby. Or _why_. She was good at _why?_, but Sherlock enjoyed that inquiring part of John's offspring.

"Lily!" he said, raising his voice slightly and slipping into an authoritative tone. "Your Daddy's going to be very cross if he comes home and finds you won't let me change your nappy."

"Dada!"

Sherlock crossed his arms pointedly.

"Where Da?" Lily asked, looking up at Sherlock with perhaps the biggest and most blue eyes Sherlock had ever seen. They were dissimilar to his own, but brighter still than John's. "And Ma?"

"Your mum and dad went on a date night," Sherlock replied patiently. "They're going to be back soon, and we need to have a clean bum for them, don't we?"

"C'ean bum," Lily repeated.

Sherlock chuckled softly. "Nappy change," he said firmly, and went to collect the nappy bag.

It was the truth that John and Mary had gone out on a date night, mostly on Sherlock's insistance. The Watson's relationship had significantly improved since the winter debacle, and even more since the birth of Lily in late March, but Sherlock had determined there was still times where they needed to get away. On those days, Sherlock demanded that John take Mary out and that he would babysit for them. Like now.

"Looooocccckk!"

Sherlock didn't particularly mind children, especially when he personally knew the parents and had a hand in raising in the child. He knew there were cases, where the parents let their children run wild and those were cases that Sherlock would rather not associate with. If a child wasn't brought up right to begin with... the terrible two's would then be terrible, he reckoned. But John and Mary were good parents, and combined with Sherlock's association, Lily was a good kid.

Asides her wailing his name as he left her in the playpen. She didn't like the playpen anymore. Sherlock didn't blame her. He wouldn't like it, either.

"_Lily_!" he called in exasperation, poking his head around the corner. "I'm right _here_. Just a _second_."

Lily spotted him and giggled, making grabby hands towards him.

Sherlock rolled his eyes, then chewed his lip contemplatively for a moment. He ducked behind the wall again and then, a second later, popped back around the corner. "Peek a boo," he said softly.

Lily giggled again, reinvested in flexing her fingers towards him. "Lock."

Sherlock shook his head mockingly, stepping the few feet away to grab the nappy bag. "We really have to change our priorities, Lily." He hefted it up over his shoulder and re-joined Lily by her playpen. "How about-" He dropped the bag and unzipped it. "- if you're good -" He rummaged around for a clean nappy, the wipes, and the powder. " - I'll get you a snack after changing your nappy." He straightened up with aforementioned items in hand, raising an eyebrow at the blonde toddler reaching for his hair.

"Snack." Lily nodded. "Be good." She stopped reaching for his hair.

"There we are." Sherlock whisked the blanket away from the chair, laying it down on the floor. "Nappy change first, snack afterwards."

Lily held up her arms to reach for Sherlock, allowing him to pick her up with ease. She was an intelligent child, with coaching from all three of them. Given the state of their lives, Lestrade, Molly, and Mrs Hudson (and on a few particular occasions, even Mycroft) all had a hand in raising her as well; it made for a fairly intelligent offspring. Either that or Lily only understood what a cookie was and that she had to be good to get one. It was moot.

Sherlock laid Lily back on the blanket. "We have really got to get you potty trained," he said, unsnapping the tiny button on Lily's tiny pair of jeans. "Should have started a few weeks ago, but John had some rubbish about how letting you age makes sure that you're emotionally ready for it," he muttered, although mostly to himself.

He didn't envy John and Mary for the potty training phase. He had heard horror stories first-hand, although mostly from Mycroft, and their mother, about his _own_ transition from nappies onwards. Apparently he had never been terribly interested in taking time away from whatever he happened to be doing to use the toilet. That bit didn't surprise him, actually.

"Oh well." Sherlock removed the dirty nappy and expertly wiped, powdered, and re-nappied Lily, all with minimal squirming or nineteen month old complaining. "_There_," Sherlock said, tugging up her trousers. "That wasn't so difficult, now was it?" He fixed the snap and reached over to press the wet wipes closed and to toss the powder back in the bag.

"Bithcuit?" Lily asked innocently.

"Yes," Sherlock agreed absently, gesturing towards the kitchen. "What kind do you reckon?" He tossed the wipes back into the bag, glancing at Lily as she wobbled back to her feet.

"Ummm... Wing?"

"Ring. Sure. What colour?" He wasn't sure if he ought to be disgusted with himself that he now understood baby talk more than he could understand the average idiot speaking, but ever since the initial first few months of Lily speaking, he actually felt rather chuffed.

"Owange! Wiggle!"

"They all have wiggles, Lily," Sherlock said patiently, gathering the dirty nappy supplies and getting to his feet. "Just a second."

"You're getting really good at this, Sherlock."

Sherlock glanced towards the doorway, pausing only a half second when he found John and Mary watching him from the doorway. "Yes... I didn't hear you come up."

"We noticed," Mary said, smiling.

"Ma?" Lily ran back into the sitting room. "Da!"

"There you are, sweetheart." John held out his arms, which Lily ran towards immediately. "How was your day with Uncle Sherlock?"

Sherlock heaved a sigh, going to toss the nappy. "I'm not old enough to be her uncle, John."

"Don't be silly," Mary said, accepting a kiss on the cheek from Lily. "Anne, she's from work, she's only twenty-one, she's an aunt twice and a great aunt once already."

"Hmm. Not sure I want to know that family dynamic." Sherlock traipsed back to the bathroom, and then returned to the kitchen after washing his hands. "Anyway, Lily was fine. She had a nap earlier, we had chicken noodle soup with a pudding cup for dinner, and she conned a biscuit out of me for a successful nappy change." He tore open the package of party rings, hooking two around his little finger.

"Sherlock..." John sighed. "What did we say about sweets?"

"It's one biscuit, and I keep my promises, John." Sherlock crouched down slightly, offering the biscuit to Lily. "Besides, she ate her dinner." Sherlock smiled at Lily and ruffled her hair, straightening up. "She's been good." He took a bite of his own biscuit and headed for the sofa. "How was your date night?"

"Good." John cleared his throat. "Really good. So, uh, thanks."

Sherlock chuckled, biscuit crumbs going tumbling to the floor. "Just remember that there's only one of me."

"What's that supposed to mean?" Mary asked.

Sherlock glanced over his shoulder. "The ratio of two kids to one of me would make me slightly less adept at babysitting."

Mary laughed, wrapping her arms around John.

"Only slightly," Sherlock said. The icing crumbled away from his biscuit just then, collapsing into a heap of pastel orange icing onto his t-shirt. "Oh, bugger!"

"Only slightly?" Mary asked teasingly.

"Buggah!"

Sherlock's eyes widened slightly and he abandoned trying to sweep the crumbs into his hand, looking up at Lily.

"_Sherlock_!"

Sherlock winced at John and Mary's combined voices. "Sorry, I forgot. My biscuit fell apart! What are you supposed to say when that happens?"

"Buggah," Lily said matter-of-factly, and nibbled on her biscuit.

"Now you're teaching her bad words. Thank you, so much."

Sherlock held up his hands. "I said I was sorry. Here." He shoved the rest of the biscuit in his mouth and stood, going over to Lily. John had just put her down and Sherlock folded down to her level, sitting back on his ankles. "Lily, love, that's a bad word. So, you can't repeat it, even though Uncle Sherlock says it, alright?" he asked gently, offering a polished smile.

Lily tilted her head. "Why?"

"Because..." Sherlock paused. "... the East Wind'll come up from the darkness and take you away if you're naughty!" he announced, wiggling his fingers into her side.

He knew that he deserved it when Lily shrieked in laughter and covered him with the biscuit crumbs sprayed from her open mouth. He knew that he deserved it, truly. So did John, and Mary, going by the laughter.

Sherlock smiled thinly, looking up at John. "There. See? It's that easy." He scrubbed his arm across his face and stood.

"Nudder bithcuit?" Lily asked, looking up at him.

"Yeah, if it's that easy," John said, crossing his arms, "tell her 'no'."

Sherlock blinked down at Lily and her big, blue eyes. He opened his mouth and then closed it again. "Yeah, I don't know that word," he said absently.

John laughed. "Yeah. Lily, darling, we have to go home. Tell Uncle Sherlock bye."

"No, dun wanna. Sday."

Sherlock smiled to himself.

"Lily," John repeated. He was slipping into his 'military' voice. His 'daddy' voice, Sherlock had called it, until John had pointed that out Sherlock was starting to use the 'daddy' voice, too.

"Nigh nigh, Lock." Lily wrapped her arms around one of Sherlock's legs.

"Uh huh." Sherlock picked her up. "Make sure Mary reads you the one with the basset hound and the kitty, yeah?"

"Yeah."

"Good girl." He kissed the top of her head and handed her over to Mary. "Let me know if you need a sitter again. Bring her by anytime."

"Or you could just come by. We're, uh, we're thinking the park next week, it's supposed to be a little warmer before the cold spell kicks back in."

"Oh. Sounds good."

"Thanks again," John hoisted the nappy bag over his shoulder. "I'll let you know. Oh, before-" He reached for the pack of nearby party rings, grabbing a couple. "Ta."

"Oi, what was all that about talking about snacks? Don't nick my biscuits."

John grinned and turned, waving as he headed down the stairs.

"Thanks, Sherlock, dear, really." Mary squeezed his shoulder. "We'll call you tomorrow."

"'kay." Sherlock saw them down the stairs and, when Lily looked over her mom's shoulder and waved, he smiled effortlessly and waved his fingers in return.

* * *

**I'm sorry but I'm not sorry. I love Sherlock taking care of babies, it's too cute. *o* Never-mind I'm being a Mary Sue, because a) my niece's name is Lily and b) I'm twenty and I have nieces/nephews who are older than me. My family dynamic is indeed a little strange. xP Anyway, just some pointless fluff for you. ^^**

**I do not own _Sherlock_. Thanks for reading!**


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